Hot water-soluble paint



Patented Feb. 13, 1945 HOT WATER-SOLUBLE PAINT Seymour D. Silver,Baltimore, Md.

No Drawing. Application August 10, 1942, Serial No. 454,253

3 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) The invention described herein may be manufactured and usedby or for the Government for governmental purposes, without the paymentto me of any royalty thereon.

This invention relates generally to cold waterinsoluble, hotwater-soluble paint which is particularly suitable for coating windowsfor blackout purposes.

The present war, which frequently necessitates that large areas beblacked out" at night so that lights from residences and buildingscannot be seen from the air, has created a demand for, an inexpensivepaint or coating which may be easily applied to window panes and likesurfaces and left thereon for such periods as may be required withoutdeterioration, and which subsequently may be readily removed with verylittle effort. This same type of paint or coating may also have a numberof other uses such as for temporarily darkening rooms so that they maybe used as photographic developing rooms, as rooms to show motionpictures or slides in, and for other purposes.

Accordingly, the primary object of this invention is to provide acoating or paint composition,

suitable for the above-mentioned purposes, which may be made fromreadily available, inexpensive ingredients, which is coldwater-insoluble so as to be durable and weather-resistant, and which ishot water-soluble so as to be easily removable when desired.

Certain other objects will, in part, be obvious, and will in part appearhereinafter.

For a more complete understanding of the nature and scope of theinvention, reference may be had to the following detailed descriptionthereof setting forth, by way of illustration, certain specificcompositions and methods of compounding the same.

The base or main component of the paint compositions of the invention isa dilute gelatin solution to which a. minute amount of a preservative,such as mercuric chloride, may be added. In addition to the gelatinsolution, the paint composition includes a small amount of a wetting oremulsifying agent. The ammonium soaps such as ammonium oleate, ammoniumpalmitate, and ammonium stearate, have been found to servesatisfactorily as the wetting or emulsifying agents. There should alsobe included in the paint compositions of the invention a small amount ofa basic reagent such as ammonia water.

Any suitable pigment may be added to the foregoing ingredients in theproper amounts. The pigment may be lampblack for blackout" paint.

fluorescent minerals for temporary signs illumi nated with ultravioletlight, or phosphorescent materials which glow in the dark. Also, thepigment may be selected on the basis of the color of illumination usedin a room. For example, if orange or red colored electric lamps or bulbsare used, a green pigment may be selected for the blackout paint. Thewavelength of light emitted from the orange or red lamps will becompletely absorbed by the green pigment. A number of similarcombinations will be suggested and occur to those skilled in the art.

As illustrative of the invention, the following specific compositionsand methods of preparing the same, are given:

(1) A gelatin base solution, containing about 0.5% by weight of gelatin,is prepared by dissolving the gelatin in hot water having a temperatureof about 190 F. To this gelatin solution may be added a minute amount ofa preservative, for example, 1:10,000 mercuric chloride.

(2) From 0.25% to 1% by weight of a wetting or emulsifying agent, whichdecomposes to an acid when the paint is dry, is added to the gelatinsolution. The wetting or emulsifying agent may be one of the ammoniumsoaps. Ammonium oleate has been found to serve very satisfactorily.

(3) From 1% to 2% of a basic reagent, such as strong ammonia water(27%), is added to the mixture. The ammonia serves to raise the pH andprevents jelling at too high temperatures.

(4) Suitable pigment in the amount of 10% is added and thoroughly mixedinto the composition.

(5) After all of the ingredients have been added, the composition is runthrough an homogenizer or colloid mill.

It will be understood that the particular sequence of adding and mixingthe ingredients outlined above may be varied so long as the desiredcomposition is obtained.

To apply the paint to window panes or other surfaces, the paint iswarmed just enough to liquefy any gelid condition, and is then eitherbrushed or sprayed onto the surfaces to be painted. To remove, the paintis simply washed with hot water, above 120 F.

It is known, from actual tests, that the paint will last at leastseveral months in service, outbe given a construction as broad as isconsistent with the state of the prior art.

What is claimed as new is:

1. A cold water-insoluble, hot water-soluble paint comprising: from 87.0to 88.75% byweight of a 0.5% water solution of gelatin preserved by theaddition of a minute amount of mercuric chloride; from 0.25 to 1.0% byweight of an ammonium soap; from 1.0 to 2.0% by weight of strong ammoniawater (about 27%); and about 10% by weight of desired pigment.

2. A cold water-insoluble, hot water-soluble paint comprisingessentially a dilute solution of gelatin in water as a majorconstituent. a small amount of ammonium soap, said amount beingsufficient for the ammonium soap to serve as an emulsifying agent andthereafter on drying of the paint for the ammonium soap to decomposeinto an acid which serves to harden the paint in a film, a small amountof ammonia water suflicient to prevent gelation of the gelatin, andsuflicient pigment to render the paint opaque.

3. A cold water-insoluble, hot water-soluble paint comprisingessentially a dilute solution of gelatin in water as a majorconstituent, a small amount of ammonium oleate, said amount beingsufiicient for the ammonium oleate to serve as an emulsifying agent andthereafter on drying of the paint for the ammonium oleate to decomposeinto an acid which serves to harden the paint in a film, a small amountof ammonia water suflicient to prevent gelation of the gelatin, andsufilcient pigment to render the paint opaque.

SEYMOUR D. SILVER.

